[djaque]

Handwavey explaination: the particles pair up because of vibrations in the crystal. It's modeled like a bunch of metal balls on with springs between them and you can imagine tapping one end and sending a wave of vibrations through. However, these springs are a bit non-linear and so I imagine that if you pack the atoms closer together then you will change the spring constant.

The other knob you can use to change the vibrations is the mass of the balls. This can be done by using different isotopes of the same element and the critical temperature goes down with mass.

[posterboy]

the particles can't pair up, because equal charges repell. That's still the virtual model.

I don't quite remember my intro to electrical components, though it's a quick read for the basics. The GP obviously knows about atom models and band gap.

The paradox bit is that, as far as I can tell pressure is roughly equivalent to heat, and heat equals decreased intrinsic conductivity. But if I imagine that high preasure restricts the absolute motion of particles, that would equal decreased resistance (like an idealized fixed suspension for your swing, that doesn't take energy out of the system).

Since Hydrogen is involved, I suppose there's a channel of Hydrogen rumps without any electrons, and the high preassure is needed to keep the hydrogen from moving apart and recombining outside the ensemble. Surely this involves some form of entanglement? Which I imagine as a kind of clockwork, all cores spinning in unison.

Haha, I have no idea what I'm talking about.

[marcosdumay]

Type I superconductors (the ones people understand) happen because electrons pair up.

The equal charges participate on the problem, but do not stop the electrons from pairing up. There is a lot of virtual particle exchange between them, but that's how forces happen. It's more correct to say that the crystal mechanically constrains the electrons into pairs than that the electrons pair with virtual particles.

(IANAP, but this one topic I have studies a little.)